Simple relations for nuclear moments

Various relations for nuclearg-factors are extended, applied and discussed in view of recent experimental data. It is shown that the additivity relation can be used such that most of the corrections to theg-factor are accounted for. The isoscalar and isovector parts of theg-factor are studied in the mass regionA≦55 under the assumption of purej ⁿ configurations. For the isoscalar part the discrepancies with experiment are compatible with those for large shell-model calculations. Good results are obtained for the isovector part of theg-factor of ground states in mirror nuclei if both Gamow-Teller matrix elements, extracted from experimentalft values with an effective coupling constant ratio for Fermi and Gamow-Teller transitions, and assumptions on the seniority of the wave functions are used.     

Effect of pre-equilibrium emission on probing postsaddle nuclear dissipation with neutrons

Using the stochastic Langevin model coupled with a statistical decay model, we study the influence of pre-equilibrium(PE) emission on probing postsaddle friction(β) with neutrons. A postsaddle friction value of(14-16.5) ×10~(21)s~(-1) and(11-13) ×10~(21)s~(-1) is obtained from comparing calculated and measured prescission neutron multiplicities of heavy fissioning systems248 Fm and256Fm in the absence and presence of the deformation factor.Moreover, it is found that a larger β is required to fit multiplicity data after the PE effect is accounted for, and that the effect becomes stronger when more energy is removed by PE particles. Our findings suggest that, to more accurately determine the postsaddle friction strength through the measurement of prescission neutrons, in addition to incorporating the contribution of PE evaporation source into the experimental multi-source analysis for particle energy spectra in coincidence with fission fragments, on the theoretical side, it is very important to make a precise evaluation of the energy that PE emission carries away from excited compound systems produced in heavy-ion fusion reactions.     

Study of the mechanisms of pre-equilibrium nuclear reactions in the microscopic approach

The mechanisms of pre-equilibrium nuclear reactions are investigated within the Statistical Multistep Direct Process (SMDP) + Statistical Multistep Compound Process (SMCP) formalism. It has been shown that from an analysis of linear part in such dependences as $$\ln \left[ {{{\frac{{d^2 \sigma }}{{d\varepsilon _b d\Omega _b }}} \mathord{\left/ {\vphantom {{\frac{{d^2 \sigma }}{{d\varepsilon _b d\Omega _b }}} {\varepsilon _b^{1/2} }}} \right. \kern-\nulldelimiterspace} {\varepsilon _b^{1/2} }}} \right]upon\varepsilon _b $$ and $$\ln \left[ {{{\frac{{d\sigma ^{SMDP \to SMCP} }}{{d\varepsilon _b }}} \mathord{\left/ {\vphantom {{\frac{{d\sigma ^{SMDP \to SMCP} }}{{d\varepsilon _b }}} {\frac{{d\sigma ^{SMDP} }}{{d\varepsilon _b }}}}} \right. \kern-\nulldelimiterspace} {\frac{{d\sigma ^{SMDP} }}{{d\varepsilon _b }}}}} \right]upon{{U_B } \mathord{\left/ {\vphantom {{U_B } {\left( {E_a - B_b } \right)}}} \right. \kern-\nulldelimiterspace} {\left( {E_a - B_b } \right)}}$$ one can extract information about the type of mechanism (SMDP, SMCP, SMDP→SMCP) and the number of stages of the multistep emission of secondary particles. In the above approach, we have discussed the experimental data for a broad class of reactions in various entrance and exit channels.     

Concentration dependence of F nuclear magnetic resonance decay shapes and second moments in bone mineral

¹⁹F nuclear magnetic resonance (NMR) spin-echoes and free induction decays (FIDs) have been observed from samples of fluoridated trabecular canine bone powder, with fluoride concentrations ([F]) ranging from approximately 10 to 33 mg F/g Ca. Curve fitting of echo envelopes and FIDs was performed using a two-component model function, where one of the components incorporates the effects of one-dimensional dipolar coupling. This function provides a good match for both echo envelopes and FIDs. Estimates of the total second moment and its homonuclear (F–F coupling) component were obtained from the fitting procedure. Based on the second moment measurements, it is argued that ¹⁹F spins in bone mineral typically experience weaker heteronuclear dipolar coupling than those in the mineral hydroxyapatite (HAP), which is often considered to be a prototype for bone mineral.     

Spectroscopic nuclear quadrupole moments

A ‘year-2001’ set of nuclear quadrupole moments, Q, is presented. Compared to the previous, ‘year-1992’ set, a major revision of the value or a considerable improvement of the accuracy is reported for ⁶ ₃Li, ₇N, ¹⁹ ₉F (197 keV, I = 5/2), ₁₁Na, ₁₃Al, ₂₁Sc, ₂₂Ti, ₂₆Fe (14 keV, I = 3/2 Mössbauer state), ₃₁Ga, ₃₂Ge, ⁷⁷ ₃₄Se (250 keV, I = 5/2 state), ₃₅Br, ₃₆Kr, ₃₇Rb, ₃₉Y, ₄₀Zr, ¹⁰⁰ ₄₅Rh, ₅₀Sn (24 keV, I = Mössbauer state), ₅₃I, ₅₄Xe, ₅₅Cs and ₈₃Bi.     

In-beam measurements of nuclear moments

Nuclear moments contribute valuable information to nuclear structure studies of nuclei under extreme conditions, such as nuclei at high angular momentum or far from stability. While the magnetic moment is sensitive to the nature of the participating nucleons (neutron or proton) the quadrupole moment is a direct measure for nuclear deformation.     

Effects of angular-momentum conservation in unified pre-equilibrium and equilibrium reaction models

The master-equation theory of precompound and compound nuclear decay is generalized to the inclusion of the conservation of angular momentum. It is demonstrated that the constructed model contains the Hauser-Feshbach, Weisskopf-Ewing as well as standard exciton models as limiting cases. This unified pre-equilibrium/Hauser-Feshbach model, which may be considered as a practicable version of the quantum-statistical, so-called AWM theory of Agassi et al., has been computationally optimized, such that the related numerical effort has become comparable to or less than that of a standard Hauser-Feshbach calculation. With this unified model the nature and importance of some spin effects in pre-equilibrium reactions has been investigated. The main conclusion from numerical calculations is that the standard precompound-model results are close to those of the angular-momentum conserving model, implying that the popular semi-classical models are quite reliable in this respect from a practical point of view.     

Year-2017 nuclear quadrupole moments

A ‘year-2017’ set of nuclear quadrupole moments, Q, is presented. Compared to the previous, ‘year-2008’ set, a major revision of the value, or an improvement of the accuracy is reported for ²₁H, ^{37, 39}₁₈Ar, ^{39, 40, 41}₁₉K, ⁶⁷₃₀Zn, ₄₈Cd, ₄₉In, ₅₀Sn (Mössbauer state), ₅₁Sb, ₈₇Fr and ₉₀Th. Slight improvements or valuable reconfirmations exist for ₄Be, ₆C, ₁₆S, ₁₇Cl, ₃₃As, ₃₅Br, ₅₃I, ₅₄Xe, ₅₆Ba, ₅₇La and ₇₂Hf.     

Nuclear moments and nuclear structure

Research activities of the Osaka Sugimoto group in the past 30 years are summarized. Developments of the perturbed angular correlation method and the new NMR method under the leadership of Sugimoto opened a wide variety of possibilities, not only in the nuclear structure study but also in studies of nuclear reactions, weak interactions and hyperfine interactions.     

The argon nuclear quadrupole moments

New standard values -116(2) mb and 76(3) mb are suggested for the nuclear quadrupole moments (Q) of the ³⁹Ar and ³⁷Ar nuclei, respectively. The Q values were obtained by combining optical measurements of the quadrupole coupling constant (B or eqQ/h) of the 3s²3p⁵4s[3/2]₂ (³P^o) and 3s²3p⁵4p[5/2]₃ (³D^e) states of argon with large scale numerical complete active space self-consistent field and restricted active space self-consistent field calculations of the electric field gradient at the nucleus (q) using the LUCAS code, which is a finite-element based multiconfiguration Hartree–Fock program for atomic structure calculations.     

Isoscalar currents and nuclear magnetic moments

We investigate meson-exchange current effects on isoscalar nuclear magnetic moments taking a one-boson exchange model. For some cases we find appreciable contributions, though the results are very model dependent. We also discuss the connection between exchange currents and the calculation of magnetic moments in the relativistic σ-ω model.     

Analysis of intermediate structures of spectral emission in pre-equilibrium nuclear reactions in the microscopic approach

The quasi-particle-phonon model of pre-equilibrium decay (QP Ph M PED) is proposed. Within this model, intermediate states are specified by the number of quasi-particles, quasi-holes and phonons. In describing nuclear relaxation we consider two types of internuclear transitions with the change in exciton number byN _ex=0, ±2 and number of phononN _ph=±1. The mixed densities of intermediate states(N _ex,N _ph,E) have been determined. An analysis has been made of the structure of the hard part of the emission spectrum in the⁶⁰Ni(p,p) and¹²⁰Sn(p,p) reaction at _p=62 MeV. This analysis suggests the importance of taking into account the transitions withN _ph=+1, along with the transitions withN _ex= +2.